An oxide is formed when an element combines with which specific element?

The formation of an oxide occurs specifically when an element reacts with oxygen. Oxides are chemical compounds that consist of at least one oxygen atom combined with another element. This reaction can take place between a metal or a non-metal and oxygen, resulting in various types of oxides, such as metal oxides (e.g., iron oxide) or non-metal oxides (e.g., carbon dioxide).

In contrast, the other elements listed—hydrogen, carbon, and nitrogen—do not produce oxides when they react with elements. For example, hydrogen forms hydrides instead of oxides, carbon can form compounds like carbides but not oxides without the presence of oxygen, and nitrogen can form nitrides. Therefore, the key to identifying an oxide is recognizing oxygen as the essential element involved in its formation.